Rotary kiln



May l1, 1965 w. J. HELFRlcl-l 3,182,980

ROTARY KILN Filed April 22, 1963 4 y@ www atent l 3,182,980 ROTARY KILN Wayne J. Helfrich, Madison, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Apr. 22, 1963, Ser. No. 274,612 Claims. (Cl. 263-33) This invention pertains to a rotary ore reducing kiln and more particularly to a rotary kiln wherein the preheating zione and reducing zone of the kiln are not physically separated.

It is the usual practice in rotary kilns to physically separate the areas where preheating and reducing of the kiln charge occur. This may be accomplished by partitioning the interior of the kiln or a separate vessel may be utilized to preheat -the charge. It is applicants intention and the general object of the subject invention to provide a rotary kiln wherein both the preheating and the reducing of the charge are accomplished within the same kiln chamber. ,4

A further object of the subject invention is to provide a rotary kiln of the hereinbefore described type wherein reducing gases are produced directly in the reaction chamber.

An additional object of the subject invention is -to provide a rotary kiln of the hereinbefore described type wherein the raw inert fuel is admitted directly into the kiln charge and the oxidizing gas is admitted into the kiln directly above the kiln charge.

These and other objects of the subject invention will become more fully apparent as the following description is read in light of the attached drawing, wherein:

FIG. 1 is a cross sectional side elevation of a rotary kiln incorporating a preferred form of the inevntion;

FIG. 2 is a cross section taken along the lines II-II ofFrG. 1; and

FIG. 3 is a cross section taken along the lines III-III of FIG. 1.

Referring to the attached drawing, the kiln shown herein for purposes of illustration is provided with an elongated cylindrical body portion 6 which defines a cylindrical chamber 7. The shell or wall 8 of the kiln may be constructed of any suitable refractory material suc-h-as re brick. Any means may be provided for supporting the kiln and as shown herein for purposes of illustration, a pair of axially spaced annular :girth rings 9 and 11 are provided about the outer peripheral surface of the kiln body. These annular rings may be supported on wheels l2'and 13 rotatably contained in conventional journal bearings 14 and 16, respectively. Rotation or oscillation of the kiln body may be provided by any conventional means and herein is shown as including a motor` generally designated 17 which is provided with a driving gear 15 in mesh with a girth gear 20 connected to the kiln body.

A stationary end piece 18 is provided a-t the discharge end of 4the kiln and a stationary end piece 19 is also provided at the intake end of the kiln. The discharge end piece 18 has an opening therein which aligns with the cylindrical chamber in the kiln so that a kiln charge generally designated 21 can pass without the kiln after it has been reduced. An opening 22 in the intake end piece 19 is in alignment with the cylindrical chamber 7 and a chute 23 may extend into the opening 22 providing a means of supplying the charge to the cylindrical chamber within the kiln. Both end pieces 18 and 19 are stationary and the kiln rotates or oscillates relative to these end pieces. The end pieces may be flanged as shown to provide a close running t with the kiln body and if necessary any conventional type of seal (not shown) may be included to seal chamber 7 from the atmosphere.

A series of circumferentially spaced longitudinally extending passageways 24 may be provided in the side wall of the kiln. A series of longitudinally spaced radially directed passageways 26 connect the longitudinal passageways with the interior of the cylindrical chamber 7. The longitudinal passageways 24 extend to one end portion 27 of the kiln body 6. An additional series of circumferentially spaced longitudinally extending passageways 28 are also provided in the side wall of the kiln. The passageways 28 are spaced radially outwardly from the passage- Ways 24 and also communicate with the chamber 7 through another series of radially directed passageways 29. The longitudinally directed passageways 28 also extend to the end portion 27 of the kiln body. It should be understood that although the invention has been shown with the passageways 24 and 28 extending within the kiln shell, it would be possible to provide pipes about the outer periphery of the kiln body without departing from the spirit of the invention.

Two pipes 31 and 32 are provided in the end piece 19 and extendtherethrough and terminate adjacent to the ends of the p assagewa'ys 24 and 28. The pipe 31 is connected with a source of oxidizing gas (not shown) and the pipe 32 is connected with a source of inert fuelj (not shown) such as a hydrocarbon fuel.

A directional manifold generally designated 33 is positioned between the end portion 27 of the kiln body and the end piece 19. This manifold 33 may be constructed of a diameter equal to the diameter of the kiln body and is provided with an opening 34 therethrough which aligns with the openings in the end pieces 19 and the cylindrical chamber 7. A first arcuate slot 36 is provided through the manifold 33 so as to align with the longitudinally extending passageways 28 and the pipe 32. This arcuate slot 36 is formed to correspond approximately to the cross sectional shape of the charge in the kiln as the kiln body rotates. An additional arcuate slot 37 through the manifold aligns with the longitudinally extending passageways 24 and the oxidizing pipe 31. As can be seen, this arcuate slot 37 is positioned to be directly above the kiln charge as the kiln rotates.

In operation, oxidizing gas is fed through the pipe 31 into the chamber 7 by way of the passageways 24 and 26 and ignited by a ame 38. When the kiln has reached the desired temperature the charge or pellets 21 are fed into the kiln through the opening 22 and are heated to reduction temperature in the preheat zone A. The pellets then pass to the reduction zone B where raw hydrocarbon is supplied directly to the pellet bed by means of the passageways 28 and 29. Because of the manifold opening 36, the raw hydrocarbon is only admitted directly to the charge bed. Furthermore, because of the configuration of the opening 37 in the manifold, the oxidizing gas is only admitted to the chamber 7 directly above the charge bed. Thermal cracking of the hydrocarbon takes place when the gas contacts the heated ore pellets producing essentially pure hydrogen and free carbon.- The hydrogen is utilized in reducing the iron ore pellets thereby forming water vapor in the charge bed. Free carbon is partially converted to carbon monoxide and hydrogen by reaction with water vapor and partially retained in the bed and circulated to the pellet bed surface by gas flow in the pellet bed. Free carbon exposed into the oxidizing gas stream is utilized by combustion to supply additional heat. The reduction reaction temperature is maintained by the neutral or slightly oxidizing flame 38 above the pellet bed by partial combustion of the off gas from the cracking and reducing operations and also by the addition of oxiding gas through the passageways 26 above the pellet bed.

With such an arrangement, it can be seen that the reducing gas is provided directly in the pellet bed by thermal decomposition on the heated kiln charge, thus restricting and reducing atmosphere to the kiln bed. The

3 off gas from the bed is directed by draft to the preheat section of the kiln where complete combustion of the gas supplies heat. The heat is utilized by conduction in the kiln shell to preheat incoming gases in the passageways 24 and 28.

Although only one embodiment of the subject invention has been herein shown and described, it will be obvious to those skilled in the art after reading this description that other modifications are possible and it is intended that all such modifications as come within a reasonable interpretation of the appended claims be covered.

Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what I claim is:

l. In a rotary ore reducing kiln having walls defining an elongated cylindrical chamber with stationary end pieces and adapted to contain a charge to be reduced contained therein, the combination comprising: means defining a plurality of longitudinally extending fluid confining passageways circumferentially spaced about the periphery of said chamber; means defining a plurality of circumferentially and longitudinally spaced openings into said chamber in iiuid communication with said passageways, said openings adapted to alternatly pass above and beneath said charge as said kiln rotates; an oxidizing gas inlet means; a fuel inlet means; and means selectively connecting said fuel inlet means to those passageways with the connected openings beneath said charge and said oxidizing gas inlet means to those passageways with the connected openings above said charge.

2. In a rotary ore reducing kiln having walls defining an elongated cylindrical chamber with stationary end pieces and adapted to contain a charge to be reduced contained in said chamber, the combination comprising: means defining a plurality of longitudinally extending liuid confining passageways circumferentially spaced about the periphery of said chamber having common ends terminating adjacent one of said end pieces; means defining a plurality of circumferentially and longitudinally spaced openings into said chamber in fluid communication, respectively, with the other ends of said passageways, said openings adapted to alternately pass above and beneath said charge as said kiln rotates; an oxidizing gas inlet means in communication with said one end piece; a fuel inlet mennsin communication with said one end piece; and means interposed between said one end piece and said said ends of said passageways selectively connecting said fuel inlet means to those passageways with the connected openings beneath said charge and said oxidizing gas inlet means to those passageways with the connected openings above said charge.

3. A rotary ore reducing kiln comprising: an outer casing defining an elongated cylindrical chamber adapted for having a charge to be reduced contained therein; nonrotating end pieces closing opposite ends of said chamber, said end pieces having a charge inlet opening and a charge outlet opening, respectively; means defining first and second groups of longitudinally extending fluid confining passageways circumferentially spaced about the periphery of said chamber having common ends terminating adjacent one of said end pieces; means defining first and second groups of circumferentially and longitudinally spaced openings into said chamber in tiuid communication, respectively, with said first and second groups of passageways, said openings adapted to alternately pass above and beneath said charge as said kiln rotates; an oxidizing gas inlet means in communication with said one end piece; a fuel inlet means in communication with said one end piece; and means interposed between said one end piece and said ends of said first and second groups of passageways selectively connecting said oxidizing gas inlet means to said first group of passageways only when the connected openings are above said charge and connecting said fuel inlet means to said second group of passageways only when the connected openings are beneath said charge.

4. A rotary ore reducing kiln comprising: an outer casing defining an elongated cylindrical chamber adapted for having a charge to be reduced contained therein; nonrotating end pieces closing opposite ends of said chamber, said end pieces having a charge inlet 4opening and a charge outlet opening, respectively; means defining first and second groups of longitudinally extending fluid confining passageways circumferentially spaced about the periphery of said chamber having common ends terminating adjacent one of said end pieces; means defining first and second groups of circumferentially and longitudinally spaced openings into said chamber in fiuid communication, respectively, with said first and second groups of passageways, said openings adapted to alternately pass above and beneath said charge as said kiln rotates; an oxidizing gas inlet means in communication with said one end piece; a fuel inlet means in communication with said one end piece; and means interposed between said one end piece and said ends of said first and second groups of passageways having a pair of circumferentially spaced arcuate slots therein aligned, respectively, with a portion of said first and second groups of passageways, one of said slots adapted to be conforming substantially to the cross sectional configuration of said charge and being in substantial alignment therewith, said other slot being circumferentially spaced substantially opposite to said one slot.

5. The rotary ore reducing kiln set forth in claim 4 wherein the passageways in each group are equidistant from the rotating axis of said kiln and the first group is radially spaced from the second group.

References Cited by the Examiner UNITED STATES PATENTS 2/17 Downs 263-33 3/31 Coley 263-33 

1. IN A ROTARY ORE REDUCING KILN HAVING WALLS DEFINING AN ELONGATED CYLINDRICAL CHAMBER WITH STATIONARY END PIECES AND ADAPTED TO CONTAIN A CHARGE TO BE REDUCE CONTAINED THEREIN, THE COMBINATION COMPRISING: MEANS DEFINING A PLURALITY OF LONGITUDINALLY EXTENDING FLUID CONFINING PASSAGEWAYS CIRCUMFERENTIALLY SPACED ABOUT THE PERIPHERY OF SAID CHAMBER; MEANS DEFINING A PLURALITY OF CIRCUMFERENTIALLY AND LONGITUDINALLY SPACED OPENINGS INTO SAID CHAMBER IN FLUID COMMUNICATION WITH SAID PASSAGEWAYS, SAID OPENINGS ADAPTED TO ALTERNATLY PASS ABOVE AND BENEATH SAID CHARGE AS SAID KILN ROTATES; AN OXIDIZING GAS INLET MEANS; A FULE INLET MEANS; AND MEANS SELECTIVE CONNECT- 